A Synergistic Photocatalytic Reduction of CO ₂ to Selective Formation of Methanol: Evaluating the Potential of <i>Ricinus communis</i> Peels Toward Green Synthesis of TiO ₂ ‐Modified g‐C ₃ N ₄

Abstract The present study synthesized TiO 2 (g)NPs(green nanoparticles) using Ricinus communis peel extract, serving as both reducing and stabilizing agents owing to the presence of biomolecules, like flavonoids (epigallocatechin gallate) and phenols (gallic acid) were identified via LC/HRMS. Characterization verified the formation of anatase TiO 2 , exhibiting a crystallite size of 14.56 nm. BET analysis indicated a mesoporous structure having surface area of 63.63 m 2 /g and pore volume of 0.11 cm 3 /g, whereas UV–vis spectroscopy indicated band gap of 3.23 eV. To enhance visible‐light activity, TiO 2 (g) was combined with g‐C 3 N 4 to create heterojunction, resulting in reduced band gap of 2.79 eV. The optimised TiO 2 (g)/g‐C 3 N 4 (1:2) composite demonstrated improved CO 2 photoreduction efficiency of 78% and a methanol production rate of 1216 µmol·g −1 ·h −1 , which can be ascribed to improved surface area of 116.66 m 2 /g. Kinetic studies indicated the highest apparent rate constant ( k app = 0.072 min −1 ) and the Freundlich adsorption model validated multilayer CO 2 adsorption on heterogeneous surfaces. This study innovatively integrates biomolecule‐rich waste for green synthesis of TiO 2 (g) NPs with a customized heterojunction design, providing a sustainable approach for effective photocatalytic reduction of CO 2 ‐to‐methanol. The combined improvement of interfacial charge separation and band alignment greatly increased the photocatalytic efficiency, showcasing dedication to sustainable practices and highlighting circular economy principles.